Idle fuel control



Dec. 8, 1959 L. c. DERMOND 2,916,270

IDLE FUEL CONTROL Filed March 24. 1958 ATTORNEY United States Patent() "i IDLE FUEL CONTROL Lawrence C. Dermond, Rochester, N.Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application March 24, 1958, Serial No. 723,196

The present invention relates to a fuel injection system of the mass air flow type utilizing a metering control valve disposed in a fuel chamber and which valve is controlled by a diaphragm device responsive to mass air flow. As set forth in copending application Serial No. 648,100 Dermond et al., it is: desirable to maintain the fuel chamber under a slight vacuum in order to remove fuel vapors which otherwise tend to accumulate and disrupt the normal function of the fuel metering valve. The'present invention relates to an improvement in the aforenoted fuel injection system in which the vacuum level Within the fuel chamber may be varied to control the idle fuel adjustment.

In the present invention a conduit communicates the fuel chamber above the fuel level with a source of manifold vacuum to draw olf fuel vapors. In addition, the present device provides a valve member in said conduit which controls an atmospheric bleed whereby the vacuum level in the fuel chamber is variable. In the present system the fuel metering valve is exposed to fuel pressure on one side tending to open the valve to bypass fuel and which valve opening pressure is opposed by the air pressure within the fuel chamber. Thus, assuming all other valve controlling forces remain constant, as the fuel chamber air or vapor pressure varies so will the quantity of fuel supplied to the engine be varied. An increase in the fuel chamber air pressure would correspondingly increase the fuel flow to the engine by reducing the quantity of fuel bypassed. It is this principle that is utilized in the present invention to rcontrol idle fuel flow. To illustrate, if a manifold depression of one inch of water was maintained in the fuel chamber it is apparent that a given pressure differential or drop between the vacuum and the fuel pressure will occur across the metering control valve and will occasion a certain rate of fuel flow. As the idle control air bleed valve is opened the absolute pressure within the fuel chamber will increase thereby reducing the pressure differential across the metering valve. Accordingly, less fuel will be bypassed by the metering valve and hence more fuel will flow to the nozzles increasing idle fuel ow. Correspondingly idle fuel flow may be decreased by reducing the atmospheric bleed to the fuel chamber.

Further objects and advantages of the present invention will be apparent from a perusal of the detailed description which follows.

Figure l is a diagrammatic representation of a fuel injection system embodying the present invention; and

Figure 2 is an enlargement of a portion of the metering valve control linkage.

The fuel injection system in general comprises an air intake passage having a throttle valve 12, a plenum chamber 14 supplied by the air intake and a plurality of individual intake passages 1S leading from the plenum chamber and respectively communicating with each of the cylinders of the engine. A fuel metering device is shown generally at 16 and includes a fuel chamber 18 having an inlet 20 the ow through -which is controlled 2,916,270 Patented Dec. 8, 1959 ICC by a conventional oat controlled fuel inlet valve Z2. A pump 24 is submerged in the fuel chamber and is adapted to pressurize the fuel and supply the same through a conduit 26 to a metering valve 28. A plurality of fuel conduits 30 communicate supply conduit 26 with individual fuel nozzles 32 disposed in the intake passages 15 proximate the engine cylinders.

Metering valve 28 includes a ball element 34 disposed within a recess 36 and which element is adapted to be moved upwardly by the uid under pressure in conduit 26 whereby a portion of the supplied fuel will be bypassed through radial passages 38 back to the fuel chamber. Opposing the fuel pressure opening movement of the valve element 34 is a control rod 40 centrally xed at its other end to a diaphragm 42 mounted in the cover wall 44 of the fuel chamber 18 and peripherally clamped to said cover wall by a cover 46. The diaphragm control rod 40 is operatively connected to the valve element 34 through an intermediate lever 48 which is part of a power enrichment mechanism 50 to be subsequently described. The upper diaphragm chamber 52 is atmospherically vented through a conduit 54 while the lower diaphragm chamber 56 is communicated by a conduit 58 with an annular vacuum chamber 60 formed in the venturi portion 62 of the air intake passage 10. As the mass or quantity of air flow increases through intake passage 10 with an opening of throttle valve 12, the vacuum force in chamber 60 and conduit 58 will be increased causing the diaphragm 42 to be moved downwardly to oppose the fuel pressure-opening of the Valve element 34 and to reduce the fuel being bypassed back to chamber 18. The result of the increase in mass air flow is therefore a corresponding increase in the quantity of fuel supplied to the nozzles 32.

The power enrichment mechanism 50 is provided in order to insure maximum fuel economy under normal operating conditions and increased fuel flow under conditions of high power demand. This mechanism includes a servo piston 64 slidably mounted in a casing 66 and dening therewith a chamber 68 connected through a conduit 70 with manifold or plenum 14. A spring 72 normally urges the piston 64 in an upwardly direction. A bell crank lever 74- is pivotally mounted at 76 and includes an arm '78 articulated to piston 64 by a link 80. The other arm 82 of bell crank lever 74 is articulated to lever 48 which, as already noted, operatively interconnects diaphragm control rod 40 and the valve element 34.

The power enrichment linkage mechanism is the subject matter of copending aplication Serial No. 723,194, filed March 24, 1958, Dermond. Lever 48 and bell crank arm 82 are pivotally connected by a pin 88. A spring 90 is looped about pin 88 and includes a first leg 92 biasing against arm 82 and a second leg 94 biasing against the underside of lever 48. Spring 90 rotatably biases lever 48 in a clockwise direction relative to arm 82. This action is then in opposition to the vacuum force in diaphragm chamber 56 tending to maintain valve element 34 in a seated position. The counterclockwise force of spring 90 is such that under normal operating conditions, i.e. pin 88 in rightmost position, it will counteract the weight of diaphragm control rod 40 and lever 48. Since the vacuum control forces acting on diaphragm 42 are relatively small it is necessary to compensate for the weights of elements acting thereon lest they upset the control of metering valve 34. Unless compensated by spring 90, the weight of rod 40 and lever 48 would urge valve 34 in a direction reducing the fuel bypassed and thereby increasing the fuel supplied to the nozzles.

A pair of spaced stops 84 and 86 are provided against which the free end of lever arm 78 is adapted to abut in accordance with the position of piston 64. Under normal operating conditions the manifold Vacuum in chamber 68 is suiciently high to overcome the spring 72 to move the piston downwardly causing the lever arm 78 to abut against the lower or economy operation stop 84. This movement of lever 74 causes the pivot point 88 between lever 48 and arm 82 to move to the right increasing the torsion on spring 90 and causing the latter to fully offset the weight of lever 48 and rod 40, supra. The rightward movement of pin 88 also shifts the fulcrum point of the lever system such that the mechanical advantage of the vacuum force acting downwardly on rod 40 is relatively decreased with respect to that of the fuel pressure urging valve 34 upwardly. The result of increased torsion on spring 90 and increased resultant effect of fuel pressure on lever 48 is to cause valve 34 to bypass more fuel thereby leaning out the fuel-air mixture for more economical engine operation.

On the other hand, under conditions of high power demand, such as occur with -a sudden depression of the accelerator pedal, the manifold vacuum in chamber 68 is reduced suiciently to permit the spring 72 to raise piston 64 until lever arm 78 abuts the upper or power stop 86 shifting the pivot or fulcrum point 88 to the left. This action decreases the torsion on spring 90 and adds the weight of rod 40 and lever 48 to the vacuum force tending to close valve element 34. Likewise the vacuum force acting through rod 40 is relatively increased with respect to the fuel force acting on valve 34, again due to changes in mechanical advantages, whereby fuel flow to nozzles 32 is increased. It is apparent that this latter operation provides fuel enrichment and hence additional power until such time as the load on the engine is suitably decreased.

The novel idle fuel flow control device will now be described. A boss 92 is formed on the fuel chamber cover 44 and is adapted to be communicated with a suitable conduit connected with a source of manifold vacuum. As set forth in copending application Serial No. 648,100, Dermond et al., filed March 25, 1957, it is desirable to eliminate the fuel vapors which tend to collect above the fuel level in chamber 18 as is particularly likely to happen under hot operating conditions. Unless eliminated such vapors interfere with the normal control of metering valve 28 by diaphragm 42. These vapors may be eliminated from the fuel chamber by maintaining a slight depression above the fuel level whereby the vapors are drawn into the manifold. The manifold vacuum in fuel chamber 18 is reduced to any desired value by any suitable orice 94 which may be disposed in boss 92.

It is apparent that with the fuel chamber maintained under a slight manifold depression, and for the moment ignoring the metering control force transmitted by diaphragm control rod 40, a pressure differential or drop will exist across the metering control valve element 34 due to the pressure of the fuel acting on one side thereof and the aforenoted manifold vacuum on the other side thereof. This pressure differential across the Valve element 34 will therefore determine the rate of fuel ow through the metering valve to the nozzles 32 with other control forces remaining substantially constant as would be the case during idling operation. By varying this pressure differential across element 34, it is possible therefore to vary the rate of fuel flow through the metering valve.

Thus, to control idle fuel ow an adjustable valve element 96 is provided in boss 92 and includes a tapered end portion 98 adapted to cooperate with an atmospheric vent port 100. The vacuum level in the fuel chamber 18 may thus be varied in accordance with the degree of opening of said atmospheric port. With the valve 96 completely blocking the atmospheric bleed port 100, a maximum vacuum force will act within the fuel chamber causing a corresponding maximum pressure drop across valve element 34. As the atmospheric vent port 100 is progressively opened by valve 98, the pressure within the fuel chamber approaches atmospheric reducing the pressure drop across valve element 34 and thereby increasing the fuel flow to the nozzles under idling conditions.

In this way a simple device is provided for controlling idle fuel flow by utilizing a control force otherwise available in the system. It is apparent that various structural modifications may be made in the subject invention Within the scope of the hereinafter appended claims.

I claim:

1. A charge forming device for an internal combustion engine comprising a common air inlet, a plurality of intake passages communicating the individual cylinders of the engine with said air inlet, throttle valve means intermediate said inlet and said intake passages for controlling the quantity of air ow through said passages, a fuel chamber, a fuel valve disposed within said charnber, a fuel nozzle disposed in each of said intake passages, a plurality of fuel conduits communicating said fuel nozzles and said fuel valve, means for controlling said valve in accordance with the mass of air flow through said air inlet, conduit means communicating said fuel chamber above the fuel level with the air inlet posteriorly of said throttle means to create a vacuum in said fuel chamber, an atmospheric bleed disposed in said conduit means, and a valve element for controlling said atmospheric bleed to vary the degree of manifold vacuum in said chamber.

2. A charge forming device for an internal combustion engine comprising a common air inlet, a plurality of intake passages communicating the individual cylinders of the engine with said air inlet, throttle valve means intermediate said inlet and said intake passages for controlling the quantity of air flow through said passages, a fuel chamber, a fuel valve disposed within said chamber, a pump for supplying fuel under pressure to the fuel valve, said fuel pressure acting on said valve to reduce fuel flow, a force proportional to the mass of air flow through the inlet acting on said Valve in opposition to said fuel pressure, a fuel nozzle disposed in each of said intake passages, a plurality of fuel conduits communicating said fuel nozzles and said fuel valve, conduit means communicating said fuel chamber above the fuel level with the air inlet posteriorly of said throttle means to create a vacuum in said fuel chamber, said vacuum force adapted to modify the actuation of said fuel valve, an atmospheric bleed disposed in said conduit means, and a valve element for controlling said atmospheric bleed to Vary the degree of manifold vacuum in said chamber.

3. A charge forming device for an internal combustion engine comprising a common air inlet, a plurality of intake passages communicating the individual cylinders of the engine with said air inlet, throttle valve means intermediate said inlet and said intake passages for controlling the quantity of air flow through said passages, a fuel chamber, a fuel valve disposed within said chamber, a pump for supplying fuel under pressure to the fuel valve, said fuel pressure acting on said valve to reduce fuel ow, a force proportional to the mass of air flow through the inlet acting on said valve in opposition to said fuel pressure, a fuel nozzle disposed in each of said intake passages, a plurality of fuel conduits communicating said fuel nozzles and said fuel valve, conduit means communicating said fuel chamber above the fuel level with the air inlet posteriorly of said throttle means to create a vacuum in said fuel chamber, said vacuum and mass air ow forces creating a pressure differential across said fuel valve which decreases fuel How as the differential increases, an atmospheric bleed disposed in said conduit means, and a valve element for controlling said atmospheric bleed to vary the pressure differential across the fuel valve to regulate idle fuel ow.

4. A charge forming device as set forth in claim 2 in which said vacuum conduit means includes an orifice for reducing the vacuum force therein, and further in which said valve element is disposed in said conduit means intermediate said orifice and said fuel chamber.

nitude of said subatmospheric pressure to regulate idle fuel ow.

References Cited in the le of this patent engine by said valve, and means for controlling the mag- 10 2,788,082

UNITED STATES PATENTS Mock June 1, 1926 Wirth Mar. 2l, 1940 Brehob Sept. 2, 1952 Vanderpoel Apr. 9, 19'57 

